Advisories

WDPN32 PGTW 050900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 13W (KUJIRA) WARNING NR 
003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8N 119.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 224 NM NORTH-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN
ELONGATED, DISORGANIZED, AND FULLY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) WEST-SOUTHWEST OF VIGAN, PHILIPPINES, WITH DEEP
CONVECTION DISPLACED TO THE SOUTHWEST QUADRANT DUE TO PERSISTENT
MODERATE NORTHEASTERLY VERTICAL WIND SHEAR (VWS). A 050209Z METOP-C 
ASCAT PASS REVEALED A HIGHLY ELONGATED LLCC, WITH PREDOMINANTLY 25-30 
KNOT WINDS IN THE NORTHERN HALF OF THE CIRCULATION AND 35-40 KNOT 
WINDS CONFINED TO THE SOUTHERN QUADRANT, CO-LOCATED WITH THE DEEPEST 
CONVECTION. THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE 
BASED ON MULTI-PLATFORM SCATTEROMETRY AND CIMSS OBJECTIVE INTENSITY 
ESTIMATES, DISCOUNTING SUBJECTIVE AGENCY FIXES WHICH ARE 
UNDERESTIMATING INTENSITY DUE TO THE DISORGANIZED CONVECTIVE 
STRUCTURE. ENVIRONMENTAL CONDITIONS ARE MARGINALLY UNFAVORABLE AS 
MODERATE VWS, DRY AIR ENTRAINMENT ALONG THE NORTHERN PERIPHERY, AND 
LAND INTERACTION IMPEDE CONVECTIVE CONSOLIDATION.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT DOMINATED BY
STRONG LOW-LEVEL SOUTHWESTERLY MONSOONAL FLOW. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 050600Z
   CIMSS AIDT: 28 KTS AT 050600Z
   CIMSS D-MINT: 34 KTS AT 050540Z
   CIMSS D-PRINT: 33 KTS AT 050600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: PROXIMITY TO LAND. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM (TS) 13W HAS MEANDERED SLOWLY
NORTHWARD IN A WEAK STEERING ENVIRONMENT OVER THE LAST 24 HOURS, AND
REMAINS QUASI-STATIONARY. OVER THE NEXT 12 TO 18 HOURS, STRENGTHENING 
SOUTHWEST MONSOON SURGE FLOW WILL STEER TS 13W EASTWARD, WITH LANDFALL 
ALONG NORTHERN LUZON EXPECTED NEAR TAU 12 TO TAU 15. THE SYSTEM WILL 
QUICKLY CROSS LUZON WHILE STEADILY WEAKENING. THE REMNANT VORTEX IS 
EXPECTED TO EMERGE OFF THE EAST COAST OF LUZON BY TAU 24 BEFORE BEING 
ACCELERATED EASTWARD INTO THE PHILIPPINE SEA ALONG THE NORTHERN 
PERIPHERY OF THE SURGING MONSOON SOUTHWESTERLIES. THE SYSTEM HAS 
ATTAINED ITS PEAK INTENSITY AND IS EXPECTED TO MAINTAIN 35 KNOTS UNTIL 
LANDFALL NEAR TAU 12. THE SYSTEM WILL WEAKEN TO 25-30 KNOTS AS IT 
CROSSES LUZON AND CONTINUE TO SLOWLY WEAKEN THROUGH THE REMAINDER OF 
THE FORECAST. UPON OFFSHORE EMERGENCE, THE LLCC IS FORECAST TO 
DEGENERATE INTO AN OPEN TROUGH WITH AN INCREASINGLY ASYMMETRIC WIND 
FIELD FEATURING 25-30 KNOT MONSOON SURGE WINDS CONFINED TO THE 
SOUTHERN PERIPHERY. BY TAU 36, THE SYSTEM WILL LOSE TROPICAL 
CHARACTERISTICS WHILE RETAINING WINDS ABOVE WARNING THRESHOLDS WITHIN 
THE ASYMMETRIC MONSOON ENVELOPE. BEYOND TAU 36, THE REMNANT VORTICITY 
WILL BE ABSORBED INTO THE EXPANSIVE CIRCULATION OF TY 12W. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT DEPICTING A SLOW 
TURN EASTWARD AND LANDFALL IN THE NEXT 12 TO 15 HOURS ALONG THE 
WESTERN COAST OF LUZON. MODELS ARE ALSO IN GOOD AGREEMENT THAT POST 
LANDFALL, THE SYSTEM WILL RAPIDLY ACCELERATE EASTWARD ALONG THE 
MONSOON SURGE AND QUICKLY MOVE INTO THE PHILIPPINE SEA.CROSS-TRACK 
SPREAD INCREASES TO 170NM BY TAU 36, WHILE ALONG-TRACK UNCERTAINTY 
INCREASES TO OVER 250NM. THE GFS, GEFS AND ECEPS MEANS REPRESENT THE 
FASTER AND NORTHERN ENVELOPE OF GUIDANCE, WHILE GOOGLE DEEPMIND AND 
EC-AIFS DEMONSTRATE A SLOWER, SOUTHERN BIAS. THE JTWC FORECAST IS 
PLACED NEAR THE AI CONSENSUS MEAN WITH MEDIUM CONFIDENCE. INTENSITY 
GUIDANCE IS IN GOOD AGREEMENT THAT THE SYSTEM WILL MAINTAIN 35 KNOT 
INTENSITY THROUGH LANDFALL BEFORE WEAKENING TO 25-30 KNOTS IN THE 
PHILIPPINE SEA. THE JTWC FORECAST IS PLACED NEAR THE GOOGLE DEEPMIND 
AND DECAY-SHIPS GUIDANCE WITH MEDIUM CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM//
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